Tripping mechanism for a plow blade

ABSTRACT

A tripping mechanism for a plow blade including an elongated, transverse flexure spring extending between the plow blade and its support structure for biasing the plow blade into the operative plowing position and forming a resilient support for the blade while it is in the operative position.

United States Patent Hanson [451 Mar. 21, 1972 Xxxw 9092 6 6 272 WWW 777 ill 6/1950 Way...... 208,583 10/1878 Frank........ 1,167,122

[54] TRIPPING MECHANISM FOR A PLOW BLADE [7 21 Inventor: Harry 1. Hanson, Minerva, Ohio 1/1916 Simmons...............................

[73] Assignee: Meyer Products, Inc., Cleveland, Ohio [22] Filed: Dec,ll,1969

211 App1.No.: 884,125

FOREIGN PATENTS OR APPLICATIONS 189,586 3/ 193? Switzerland.........................,.....

3/1953 564,915 9/l944 En [52] US. VL,172/264, 172/269,

.37/41, 42 R, 42 VL, 35, 50;

Primary Examiner-Robert E. Pulfrey Assistant Examiner-R. E. Suter Attorney-Meyer, Tilberry and Body [51] [58] FieldofSearch..l................

7] ABSTRACT A tripping mechanism for a plow blade including an elongated, transverse flexure spring extending between the plow blade and its support structure for biasing the plow blade into References Cited UNITED STATES PATENTS the operative plowing position and forming a resilient support for the blade while it is in the operative position.

37/42 R ..........l72/265 .37/42 VL UX 8 Claims, 19 Drawing Figures 3,426,458 2,296,175 9/1942 Morkoski.. 1,379,363 5/1921 PATENTEDMARZI 1972 Y 3,550,054

' SHEET 1 UF 4 INVENTOR.

ATTORNEYS HARRY I. HANSON PATENTEDMARZ] I972 sum 2 or 4 I NVEN TOR.

FIG. 5

FIGI.4

'IIIIIIIII/ 32/ FIG. 6

ATTORNEYS PATENTEDMARZ] I972 3,650,054

sum u or 4 (PRIOR ART) INVENTOR. HARRY I. HANSON ATTORNEYS TRIPPING MECHANISM FOR A PLOW BLADE This invention relates to the art of plow blades, and more particularly to a tripping mechanism for a plow blade.

The invention is particularly applicable for use in a snow plow of the type mounted on the front of a vehicle to remove snow and debris, and it will be described with particular reference thereto; however, it will be appreciated that the invention has much broader applications and may be used as a tripping mechanism for various plow blades.

In removing snow and debris from a roadway, it has become common practice to mount a plow blade onto the front of a vehicle so that the blade moves the snow or debris sideways away from the roadway. Such plow blades have a lower scrapping or plowing edge pointing outwardly toward the direction of plowing and an upper curved moldboard extending from the plowing edge to a position above or forward of this plowing edge. When this plowing edge encounters an obstruction in the roadway, a tripping mechanism, incorporated with the plow blade mounting structure, allows the'blade to pivot forwardly against the action of tension springs so that the edge can pass over the obstructiomThe springs employed by the tripping mechanism lift the plow blade back into its operative, plowing position after the obstruction has been cleared. A common tripping mechanism includes two coil tension springs extending between the back of the plow blade and the support structure connected to the vehicle. These springs are stretched during the tripping action, and the stress in the springs lifts the blade into its operative position. In this mechanism, stationary cushions orstops are provided to locate the plow blade in its operative position. These cushions or stops may include bumpers or other arrangements for decreasing the shock created when: the blade moves abruptly from the tripped position to the operative, plowing position. This rapid movement is essential so that the blade assumes its operative position as soon as possible after passing over the obstruction. Otherwise, the blade will leave a large deposit of snow or debris adjacent each obstruction. This would result in unsatisfactory plowing of the roadway. The use of tension springs for pulling the blade against stops to define the plowing position has certain limitations.

The coil springs pull the blade against the stop with a large force to hold the blade somewhat rigidly in the plowing position. This force varies with factors, such as blade size, vehicle power and intended use; however, in some instances it is approximately 300 pounds. Consequently, the tension springs are prestressed and stretched when the blade is in the plowing position. During tripping, the springs are stretched even further to load the springs with a force as high as 1000-1300 pounds. This is a relatively high stress on the tension coil springs. Also, this stress is caused by the amount of stretch required to accommodate the movement of the blade into its tripped position. This stretch may be over 7 inches. Because of these loading forces and repeated, extensive stretching of the heavy duty coil springs, relatively expensive springs must be used, and they are subjected to possible failure and/r axial deformation. It is difficult to obtain a spring which will create the necessary high forces and still allow the necessary amount of stretch.

Since the blade is pulled into contact with a stop during plowing to create a force holding the blade, when snow or other debris moves up the front, forwardly curved surface of v the blade, theblade can not pivot backwardly so it tends to raise from the roadway. To overcome this difficulty, the weight of the blade and its support structure is increased. This tends to load the bearing used to pivotally mount the blade. By using coil springs, the load on the blade mounting bearings is increased due to the characteristic of the spring which increases the force of the blade at a high rate directly proportional to the spring elongation and, thus, the blade movement.

The present invention is directed toward an improved tripping mechanism which eliminates the necessity for coil springs, overcomes the disadvantages of prior tripping mechanisms, provides rapid movement of the blade from the tripped position to its operative position, and provides an inherent shock absorbing characteristic in the tripping mechanism itself.

In accordance with the present invention, the tripping mechanism includes an elongated, transverse flexure spring extending between the back of the plow blade and its support structure. A lever is employed for connecting the spring itself onto the plow blade so that the spring can flex transversely without requiring longitudinal stretching of the spring during the tripping operation.

The transverse flexure spring may take a variety of mounting arrangements when connecting the plow blade and its support structure. In addition, the spring itself may have a variety of constructions, such as a leaf spring, a multi-leaf spring, a rod spring, and a flat spring with transverse undulations, to name a few. The term transverse flexure spring" is used to indicate a spring wherein the bending action of the spring fonns the essential spring action. This is distinguished from a coil spring wherein the spring action is primarily obtained from elongation or compression of the spring in an axial direction.

The primary object of the present invention is the provision of a tripping mechanism for a plow blade, which mechanism uses an elongated, transverse flexure spring for biasing the blade into its operative position.

Another object of the present invention is the provision of a tripping mechanism for a plow blade, which mechanism uses an elongated, transverse flexure spring for biasing the blade into its operative position and wherein the spring performs a shock absorbing function.

Still another object of the present invention is the provision of a tripping mechanism for a plow blade, which mechanism can be used with existing plow blades and their support structure.

Yet another object of the present invention is the provision of a tripping mechanism as mentioned above, which mechanism provides a controlled rate of return of the blade from its tripped position to its operative position. This controlled rate includes a rapid movement from the tripped position and then relatively slow movement into the actual operative position.

Still another object of the present invention is the provision of a tripping mechanism for a plow blade, which mechanism has longer spring life and increased life of the pivotal connection between the plow blade and its support structure.

Another object of the invention is the provision of a spring tripping mechanism for a plow blade, which mechanism tends to hold the blade down during plowing.

Yet another object of the present invention is the provision of a tripping mechanism for a plow blade, which mechanism employs a transverse flexure spring formed with transversely extending torsion elements.

These and other objects and advantages will become apparent from the following description taken together with the accompanying drawings in which:

FIG. 1 is a pictorial view illustrating, somewhat schematically, the environment to which the present invention is directed;

FIG. 2 is an enlarged side elevational view illustrating the preferred embodiment of the present invention;

FIG. 3 is a side elevational view showing a flexure spring used in the preferred embodiment, as illustrated in FIG. 2;

FIG. 4 is a partial top view taken generally along line 4-4 of FIG. 1;

FIG. 5 is an enlarged view taken generally along line 5-5 of FIG. 2;

FIG. 6 is an enlarged cross-sectional view illustrating a modification of the preferred embodiment of the invention as illustrated in FIG. 2;

FIG. 8 is an enlarged pictorial view showing the modification of a spring for use in the present invention;

FIG. 9 is a side elevational view illustrating, somewhat schematically, another aspect of the present invention;

FIG. 7 is a top view taken generally along line 7-7 of FIG.

FIG. is a partial cross-sectional view taken generally along line 10l0 of FIG. 9;

FIG. 11 is a partial cross-sectional view taken generally along line 11-11 ofFIG.10;

FIG. 12 is an enlarged cross-sectional view taken generally along line 12-12 ofFlG. 9;

FIG. 13 is a cross-sectional view taken generally along line l3-13 of FIG. 1 1 showing the plow blade in an alternate position;

FIGS. 14-17 are schematic views illustrating other modifications of the present invention;

FIG. 18 is a schematic view showing an operating characteristic of a prior art tripping mechanism; and,

FIG. 19 is a schematic view showing an operating characteristic of one aspect of the present invention.

Referring now to the drawings wherein the showings are for the purpose of illustrating preferred embodiments of the invention only and not for the purpose of limiting same, FIG. I shows a blade A, of the type adapted to be connected onto the front of a vehicle B, and raised and lowered by an appropriate lift device C. Blade A is used to remove snow or other debris D from a roadway E which contains various obstructions, such as a raised portion F. The present invention relates to an improved mechanism for tripping the snow blade A as it passes over the obstruction F during the plowing operation.

Referring now to FIGS. 2, 3, 4 and 5, the blade A includes a forwardly curved moldboard 10 having a top edge 12 and a bottom edge 14. Adjacent the bottom edge there is provided a transversely extending scrapping, or plowing edge, 16 secured onto the moldboard 10 by a number of transversely spaced bolts 18, only one of which is shown. These bolts coact with a transversely extending support bracket 20 to secure the scrapping edge 16 onto the edge 14. Blade A is mounted on a support structure to pivot about an axis 30. The support may take a variety of forms; however, in the illustrated embodiments it includes two forwardly extending elements 32, 34. Blade A forms an included angle between the back of the moldboard 10 and element 32 with the apex of this angle being generally located at axis 30. In accordance with normal practice, the support structure formed from elements 32, 34 is pivotally mounted on the front of the vehicle and an appropriate journal, such as journal 36 shown in FIG. 1, which allows blade A to be moved upwardly away from the roadway by the lift device C or by upward thrust on the blade during the plowing operation.

The present invention relates to a tripping mechanism 40 which is formed by identical components secured to elements 32 and 34. Since these components are substantially identical, only the components associated with element 32 will be described. This description will apply equally to the components secured onto the element 34. The basic feature of the present invention is the use of an elongated, flexure spring 42 which may take a variety of forms, such as a leaf spring, a rod spring, a multi-leaf spring, and a generally flat spring having transverse undulations, to name a few. A transverse flexure spring is a spring wherein the spring action is primarily caused by transverse movement of its ends with respect to its axis, as opposed to a spring action caused by elongation or stretching of the spring along its axis.

In accordance with the embodiment of the invention illustrated in FIGS. 2-5, the flexure spring is designated 42 and includes spaced ends 44, 46. Between the ends the generally flat spring is formed into a series of transversely extending convolutions 50 formed from transverse elements 50a connected at alternate ends to opposite adjacent arms 50b, 500, as shown in FIG. 5. This spring has a relaxed contour such as shown in FIG. 3 which is curvilinear with an offset facing to the right. To assemble the spring with respect to the plow blade A, end 44 is secured onto element 32 by a clamp plate 54 and a bolt 56. This rigidly secures the spring 42 onto element 32 in a manner to extend the spring so that the element 32 is substantially tangential to the bottom of the spring. Spring 42 is flexed transversely by unrolling it along the element 32. During flexing of the spring in a direction generally perpendicularly to the flat sides or faces of spring 42, the general spring action is a bending action. This bending action is, in the preferred embodiment, a combination of torsion imposed upon transverse elements 50a and flexing imposed upon arms 50b, 50c. The upper end 46 of spring 42 is secured onto the rear of board 10 by a lever 60 having a first pivot pin 62 connected onto the spring end 46 and a second pivot pin 64 joumaled onto the blade between spaced support plates 66, 68.

Lever 60 includes a tail 70 which is long enough to extend over retaining pin holding lugs 72, 74, 76 and 78 provided in flanges 66, 68, in a generally circular pattern around pin 64. Each of these lugs is substantially identical and includes a sleeve 80, a detent ball 82 and a detent spring 84, shown best in FIG. 5. To control the pivotal movement of lever 60, two stop pins 90, 92 are received within lugs 72, 78, respectively. These pins each include a head 94 and a detent groove 96 which coacts with detent ball 82 to hold the stop pins in the respective lugs. Of course, various other structures could be utilized for providing stops to coact with the lever 60. Pin limits the counterclockwise rotation of lever 60, and pin 92 limits the clockwise rotation of this lever, as shown in FIG. 2. In practice, it is possible to use only the pin 90 or, in some instances, use no pins for controlling the movement of lever 60. By changing pin 90, the amount of tripping movement of blade A is varied. By changing pin 92, the amount of preload on the blade during plowing can be controlled. This provides a convenient manner of adjusting the spring action for varying conditions.

The operation of the tripping mechanism 40 can be best described in connection with FIG. 2. The solid line position of plow blade A, designated 1, is the normal plowing position for the blade. In this position, the spring 42 is somewhat uncoiled from its relaxed position shown in FIG. 3 and bears against a plate 100 secured onto flanges 66, 68. When edge 16 contacts an obstruction within the roadway, blade A trips into the tripped position, shown in phantom lines and designated II. In this position, the spring 42 is further unwound and flexed by lever 60 which is pivoted into engagement with pin 90 to control the extent of the tripping movement. If pin 90 were in another lug, the outward tripping motion would further uncoil the spring 42 or limit the movement of blade A into its tripping position. The amount of spring uncoil also changes theinitial force applied to the blade when the obstruction is cleared. As can be seen, the end 46 of spring 42 moves a substantial distance and uncoils the spring to provide a gradual controlled movement of blade A which may not be a straight line function of the distance which end 46 actually moves. As the blade moves into the tripped position, elements 32 and 34 may pivot upwardly slightly about journal 36.

Upon passing the obstruction, spring 42 again recoils and abruptly pulls the blade A toward the initial position I. When the blade reaches this position, plate 100 contacts the spring and forces the blade back into a retracted position III, shown in phantom lines. This deforms the spring 42 and provides a cushion which absorbs shock of the backwardly moving blade. Thereafter, the deformed spring 42 assumes its normal position shown in solid lines and determined by pin 92, which forces the blade into the plowing position I.

Since the spring 42 is uncoiled when end 46 is moved by the blade A during tripping, the force exerted upon lever 60 tending to restore the blade to its upright plowing position is increased non-linearly with the higher increase being at the end of the movement whenthe blade is fully tripped. In this manner, a high force is imposed immediately to restore the blade to the plowing position, and the force decreases more rapidly than the actual movement of blade A toward its operative position.

Referring now to FIGS. 6 and 7, a second preferred embodiment of the invention is illustrated. In accordance with this embodiment, the elongated flexure spring is a leaf spring having spaced ends 112, 114 secured onto element 32 by a pin and lever 60 by a pin 122. Operation of this preferred embodiment of the invention is substantially identical to the operation of the embodiment illustrated in FIGS. 2-5. However, there are no separate transverse elements to provide a torsion spring action. Although various spring constants could be provided in the leaf spring 110 or the fiat spring 42, in accordance with the preferred embodiment of the invention, the average spring constant is at least 40 pounds per inch of movement of end 46 as it coils and uncoils the spring. It is anticipated that this average spring constant will be approximately 75-100 pounds per inch of movement of end 46.

Referring now to FIG. 8, a modified elongated flexure spring 130 is illustrated. This spring is generally flat and includes spaced notches 132 along one side and spaced notches 134 along the opposite side. These notches are cut from the spring and coact to form interconnected transversely extending convolutions 136 which are similar to the convolutions 50 utilized in spring 42. These convolutions are formed by transverse elements 136a and interconnecting arms 136b, 1366. By using transversely extending convolutions 136, when the flat spring is flexed transversely to its length and perpendicular to one of its flat surfaces, the transverse elements 136a have a torsional stress. This torsional stress of the spring provides an improved flexing characteristic for the spring.

Referring now to FIGS. 9-13, there is illustrated a brake means 140 for slowing down the movement of the plow blade A as it is shifted into its operative, plowing position. This brake means is effective to modify the velocity of the plow blade only in the vicinity of the operative position. In accordance with the illustrated embodiment, the brake means includes a friction plate 142 secured onto the back of blade A. This plate extends between two biased brake shoes 144, 146, each having divergent entrant flanges 148. Support plates 150, 152 are fixedly attached onto support element 32 to carry a plurality of springs 154. These springs bias the brake shoes 144, 146 toward each other. When the brake is tripped, friction plate 142 is pulled from the shoes 144, 146. This releases the blade A for uninhibited tripping action. After the blade has been tripped and it is being forced backwardly into the operative position by spring 42, or another spring, there is initially uninhibited movement of the blade. As the blade approaches the operative position, however, friction plate 142 enters the space between the brake shoes 144, 146. This immediately applies a braking action to the backwardly moving plow blade. Consequently, the plow blade is decelerated as it is moved into its final position. This type of braking action or brake means can be incorporated into various tripping mechanisms utilizing a flexure spring or other springs, such as coil springs. Of course, other modifications could be made in the brake means as long as the braking force is applied during the terminal travel of the blade toward its operative position, as opposed to application of this force over the complete travel of the blade. In practice, the brake means 140 is constructed to be operable only during approximately the last 30 of movement of the blade toward the operative position. In accordance with the preferred embodiment the brake means 140 is operative in the range of to 40 prior the blade assuming its operative position.

FIGS. 14-17 illustrates various modifications of a tripping mechanism employing a transverse flexure spring, such as a leaf spring. These particular embodiments differ from the preferred embodiment as best illustrated in FIGS. 2 and 6 but not employing an uncoiling action to the transverse flexure spring. This uncoiling action has the advantage of providing a more gradual programming for movement of the blade. Referring now to FIG. 14, a transverse flexure spring 160 having ends 162, 164 and an intermediate generally straight portion 166 is connected between the support element 32 and blade A by a pivoted lever 168, generally corresponding to lever 60 of the preferred embodiments. In FIG. 15, spring 170 having spaced ends 172, 174 is connected onto support element 32 by a bracket 176. A lever 178 connects the end 174 with the blade A. Referring now to FIG. 16, a spring 180 includes spaced ends 182, 184 and is connected onto the blade A by lever 186. Referring now to FIG. 17, the transverse flexure spring 190 having spaced ends 192, 194 is connected onto the plow blade A by an elongated lever or bar 196. The bar 196 pulls spring 190 forward into the tripping position to stress the spring. When the plow blade moves from the tripped position into the operative position, lever or bar 196 forms a means of transmitting force in both directions to the spring 190. Consequently, a shock absorbing characteristic is employed. In the embodiment shown in FIGS. 14-17, pin 192 can be used to prestress the transverse flexure springs for holding the blade A rigidly in the plowing position when the springs are assembled as illustrated in the figures. Also, a fixed stop could be used to provide a pre-stress in the transverse flexure spring.

When using the preferred embodiment of the present invention as illustrated in FIGS. 2 and 6, the tripping mechanism tends to maintain the blade in contact with the roadway, especially during heavy plowing of wet snow. This concept can best be understood by first discussing the operation of the common coil spring tripping mechanism. Such a mechanism is schematically illustrated in FIG. 18 wherein a coil spring 200 pulls the blade A against stop 202 for locating the blade in its plowing position. When snow is being plowed, snow moves upwardly along a path indicated by the arrow S. Because of the stop 202, the resulting force created by the upward movement of the snow as it approaches the upper portion of the blade is in a generally upward direction indicated schematically by arrow F This tends to raise the blade edge 16 from the roadway. To counteract for this, the plowing device and its support structure are generally weighted. When using the preferred embodiments of the invention, schematically illustrated in FIG. 19, as the snow moves upward along the moldboard of blade A, the spring has tendency to flex and allow backward movement of the blade. This creates a resulting force F acting against the resiliency of spring 110 which force is generally downward in direction from the upper portion of the blade. In this manner, the edge 16 tends to remain on the roadway during plowing as the blade moves slightly rearward. FIG. 19 illustrates one advantage of the preferred embodiments of the present invention. The use of the term resulting forces" is employed only to show the actual operating characteristics of the plow and not in the purely technical sense. In essence, the use of the spring 110 allows the blade A to flex backwardly upon applying forces at the top of the blade. This then produces a force downwardly. In the prior art shown in FIG. 18, the stop 202 does not allow this backward movement of the blade so the snow moving upward to the top of the blade surface can only pivot the blade around the vehicle pivot journal 36. This creates upward movement of element 32 and movement of the edge 16 away from the roadway.

Several elongated transverse flexure springs have been illustrated and described herein, and they have all provided the primary springing action in a direction binding the elongated spring. Of course, other such transverse flexure springs can be used, such as a heavy coil spring having a preformed shape similar to spring 42 shown in FIG. 3 with the dimensions and material of the spring causing a high spring constant in the binding direction.

Having thus described my invention, 1 claim:

1. A tripping mechanism for a plow blade member having a lower edge and being mounted on a support member to pivot about an axis generally parallel to said edge, said blade member forming an upper included angle with said support member with said axis being generally at the apex of said angle, said blade member having an operative position with said included angle at a given value and a pivoted tripped position with said blade member pivoted to increase said included angle, said tripping mechanism comprising: an elongated, transverse flexure spring having first and second ends and a bending spring action caused by relative movement of said spring ends generally transverse to said spring; first means for connecting said first end to said support member; second means for connecting said second end to said blade member; said first and second connecting means positioned to locate said spring within said included angle and for causing relative movement of said spring ends transverse to said spring when said blade member is shifted from said operative to said tripped position whereby said spring is bent to create a restoring force to shift said blade member from said tripped position to said operative position, said second spring connecting means being a lever having a first end pivotally mounted on said blade member about a second axis generally parallel with said blade mounting axis and a second end pivotally mounted onto said second end of said spring about a third axis generally parallel to said blade mounting axis and allowing said second end of said spring to abut and bias said blade into its operative position.

2. A tripping mechanism as defined in claim 1 wherein said second axis is generally below said third axis.

3. A tripping mechanism as defined in claim [wherein one of said spring connecting means includes means for fixedly securing one of said spring ends to one of said members.

4. A tripping mechanism as defined in claim 1 wherein said spring comprises a plurality of transversely extending undulations.

5. A tripping mechanism as defined in claim 1 wherein said spring has an average spring constant of at least about 40 pounds per inch of movement of one of said spring ends transversely of said spring.

6. A tripping mechanism as defined in claim 1 wherein said spring has a curvilinear shape when said plow blade member is in said operative position.

7. A tripping mechanism as defined in claim 6 wherein said curvilinear shape extends from said support member toward said blade member 8. A tripping mechanism as defined in claim 7 wherein said curvilinear shape is concave with respect to said apex. 

1. A tripping mechanism for a plow blade member having a lower edge and being mounted on a support member to pivot about an axis generally parallel to said edge, said blade member forming an upper included angle with said support member with said axis being generally at the apex of said angle, said blade member having an operative position with said included angle at a given value and a pivoted tripped position with said blade member pivoted to increase said included angle, said tripping mechanism comprising: an elongated, transverse flexure spring having first and second ends and a bending spring action caused by relative movement of said spring ends generally transverse to said spring; first means for connecting said first end to said support member; second means for connecting said second end to said blade member; said first and second connecting means positioned to locate said spring within said included angle and for causing relative movement of said spring ends transverse to said spring when said blade member is shifted from said operative to said tripped position whereby said spring is bent to create a restoring force to shift said blade member from said tripped position to said operative position, said second spring connecting means being a lever having a first end pivotally mounted on said blade member about a second axis generally parallel with said blade mounting axis and a second end pivotally mounted onto said second end of said spring about a third axis generally parallel to said blade mounting axis and allowing said second end of said spring to abut and bias said blade into its operative position.
 2. A tripping mechanism as defined in claim 1 wherein said second axis is generally below said third axis.
 3. A tripping mechanism as defined in claim 1 wherein one of said spring connecting means includes means for fixedly securing one of said spring ends to one of said members.
 4. A tripping mechanism as defined in claim 1 wherein said spring comprises a plurality of transversely extending undulations. Pg,18
 5. A tripping mechanism as defined in claim 1 wherein said spring has an average spring constant of at least about 40 pounds per inch of movement of one of said spring ends transversely of said spring.
 6. A tripping mechanism as defined in claim 1 wherein said spring has a curvilinear shape when said plow blade member is in said operative position.
 7. A tripping mechanism as defined in claim 6 wherein said curvilinear shape extends from said support member toward said blade member.
 8. A tripping mechanism as defined in claim 7 wherein said curvilinear shape is concave with respect to said apex. 